1. Field of the Invention
This invention relates to a novel compound having an antitumour activity and a process for preparing this compound.
2. Description of the Background
Camptothecin is a penta-cyclic alkaloid isolated from barks, roots, fruits, or leaves of camptotheca acuminata. This compound is known to exhibit an antitumour activity because of its capability of inhibiting nucleic acid synthesis. According to the results of clinical tests conducted in the United States, however, the compound was found to have a problem in view of safety, and its research and development as a medicine have been discontinued.
Thereafter, research on derivatives of camptothecin possessing better activity and reduced toxicity has been undertaken worldwide. However, no report has surfaced on the derivative with satisfactory clinical results.
The present inventors have conducted extensive studies for the purpose of obtaining camptothecin derivatives with more excellent activity and higher safety, and found novel compounds with activities superior to that of camptothecin. This finding has led to the completion of this invention.